Gamasutra has also reported up to 25 employees may have also been let go from the company, mainly in the hardware and Android development divisions.

Holtman acted as one of the company's primary points of contact for devs using Valve's digital distribution platform Steam, playing a key role in developer relations at the studio, and has worked at the development giant since 2005.

The news of his departure will come as a shock to many, given has important role at the firm and the continued success of Steam, a platform driving the success of the PC games market.

Develop has contacted Valve for more details on the matter and we will update the story as soon as we learn anything.

Update:

An examination of Valve's official employee list suggests these people are part of those leaving the company. Jason Holtman was also excluded from this list.

Moby Francke: Character designed on Half-Life 2 and Team Fortress 2

Keith Huggins: Joined from "world of feature film special effects, previously working at Industrial Light and Magic

Tom Leonard: worked on design and technology for Half-Life 2, Episodes One and Two, and Left 4 Dead.

Realm Lovejoy: Works in computer animation and worked on Portal.

Marc Nagel: Previously worked on Half-Life, Opposing Force and Counter-Strike as test lead

Bay Raitt: Previously led the creation of Gollum's facial system for The Lord of the Rings trilogy

Elan Ruskin:Engine programmer and gameplay developer

Matthew Russell: Animator

Update 2:

Valve has not yet responded to Develop's request for comment, but Gabe Newell told Engadget that there has been no major change of plans at the company.

"We don't usually talk about personnel matters for a number of reasons. There seems to be an unusual amount of speculation about some recent changes here, so I thought I'd take the unusual step of addressing them," said Newell.

"No, we aren't canceling any projects. No, we aren't changing any priorities or projects we've been discussing. No, this isn't about Steam or Linux or hardware or [insert game name here]. We're not going to discuss why anyone in particular is or isn't working here."